This invention relates to a method of operating a fluidized bed reactor and, more particularly, to a method for improving the reaction efficiency of same.
The use of fluidized bed reactors, in the form of combustors, gasifiers or steam generators has been recognized as an attractive means of generating heat. In the operation of these reactors air is passed through a bed of particulate material which includes a mixture of inert material, a fuel material such as high sulfur, bituminous coal and, usually, adsorbent material for the sulfur oxides formed as a result of the combustion of the coal. As a result of the air passing through the bed the bed is fluidized which promotes the combustion of the fuel. The basic advantages of such an arrangement are many and include a relatively high heat transfer rate, a substantially uniform bed temperature, combustion at relatively low temperatures, ease of handling the fuel materials, a reduction in corrosion and boiler fouling and a reduction in boiler size.
However, in these types of methods the quantity and velocity of the air supplied to the bed must be sufficient to maintain same in a fluidized condition and, as a result, a portion of the particulate bed material is entrained by the air passing through the bed and includes unreacted fuel and adsorbent material. In some methods, the air passing through the bed along with the gaseous products of combustion and the particulate material entrained therein is passed to a dust collector, or the like, for separating the solids from the gases, and the solids are then discarded or passed to an external apparatus not connected with the fluidized bed process. Since a good percentage of the particulate material thus discarded contains unreacted solids, this lowers the potential reaction efficiency of the process.
In other methods of this type, the separated solids are injected back into the bed so that the unreacted fuel will hopefully combust along with the other particulate fuel in the bed. However, fuel material is still carried out of the bed in an unreacted state, which results in a less than optimal fuel burning and renders the system sensitive to fuel sizing and ash content.